During CPB, tissue perfusion injury occurres even ii perfusion pressure is maintained. Though vaso-dilator (VD) and -constrictor (VC) are clinically administered ii bypass flow is maintained, they may restore perfusion pressure without improving tissue perfusion. We evaluated influence of VD and VC on the whole body during CPB. Forty-eight adult cases of valvular disease without blood transfusion during moderately hypothermic CPB were divided into 4 groups, depending upon whether administered or not (1: VD, 2: VD and VC, 3: VC, and 4: none; n = 5, 9, 14, 20). Bypass flow and aortic pressure were maintained at 2.4 l/m2/ min and 50∼ 90 mmHg. Body weight, dilution, hematocrit level, CPB and aortic clamp duration, blood temperature, bypass flow, perfusion pressure, base excess level during CPB, cardiac index, arterial and mixed venous oxygen pressure, and alveolar-arterial oxygen distribution after CPB were comparable among the four groups. However, blood lactate level returnig to the ward is higher (1, 2, 3 vs 4: 7.5 +−1.0, 7.0 +−1.8, S.6 +−2.1 vs 5.5 +−1.9 ml/kg; 1 vs 4: p<0.05, 2 vs 4: p=0.05) and time to extubation was longer (11.1 +−4.1, 13.0+−4.4, 13.3+−4.8 vs 9.0+−5.1 hrs; 2 vs 4, 3 vs 4: p<0.05) in the administered groups than in the control group, whereas blood lactate level on extubation and blood creatinine level on post-operative day 1 were comparable among the groups. In conclusion, VD and/or VC administration during CPB deteriorates the body oxygen metabolism, which implies tissue perfusion, and may make the complication worse induced by hypoperfusion arisen during CPB.